Air Traffic Control:

FAA Plans to Replace Its Host Computer System Because Future Availability Cannot Be Assured

AIMD-98-138R: Published: May 1, 1998. Publicly Released: May 1, 1998.

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Joel C. Willemssen
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Pursuant to a congressional request, GAO provided an assessment of the Federal Aviation Administration's (FAA) Host Computer System (HCS), focusing on: (1) whether HCS has been meeting availability requirements; and (2) issues that may affect FAA's ability to ensure HCS' availability in the future.

GAO noted that: (1) air traffic controllers in FAA's 20 en route centers control aircraft over the continental United States in transit and during approaches to some airports; (2) HCS is the key information processing system in FAA's en route environment; (3) for the last 3 years, HCS has not met its availability requirements; (4) FAA has specified a HCS system availability requirement of 99.998 percent; (5) HCS did not meet this requirement in 1995, 1996, and 1997, with average availabilities of 99.972 percent, 99.984 percent, and 99.982 percent respectively; (6) it also did not meet it in the first 2 months of 1998, with an average availability of 99.992 percent; (7) one key issue affecting HCS' future availability is the shortage of critical spare parts; (8) given that HCS hardware is approaching the end of its expected life cycle, IBM calculated end-of-service dates for each HCS subsystem based on failure rates, available spares, engineering support, plant maintenance, and project demand; (9) IBM identified eight key hardware units, including the main processor, that will reach their end-of-service dates on or before December 31, 1999; (10) to prolong the life of the current inventory of spare parts, in December 1997, FAA implemented a more conservative replacement policy for Thermal Conduction Module (TCM) parts; (11) under this new policy, TCM parts are not automatically replaced after experiencing two minor problems, as they were under the prior policy; (12) a second key issue that could affect HCS' availability is the year 2000 computer problem; (13) while FAA officials expressed confidence that they had resolved date dependencies in HCS' operating system and application software, IBM reported that it has no confidence in the ability of the HCS processor's microcode to survive the millennium date change because it no longer has the skills or tools to properly assess this code; (14) IBM has therefore recommended that FAA purchase new HCS hardware; and (15) because of concerns about the availability of spare parts and the year 2000 issue, FAA initiated the Host and Oceanic Computer System Replacement program to replace all HCS processors in its 20 en route centers and training and technical support centers by October 1999.